Airfoil/Flap Example Case

Airfoil/Flap Example Case∗

The NPARC Alliance

NASA Glenn Research CenterCleveland, Ohio

USAF Arnold Engineering Development CenterTullahoma, Tennessee

∗This is an unnumbered version of this document, created May 27, 2009. Please send corrections, additions, ideas,etc., to Dennis Yoder at [email protected] or Mark Fisher at [email protected].

Contents

1 Introduction 1

2 Creating the .cgd File 3

3 Using GMAN 73.1 Opening the File . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73.2 Cutting the Hole . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83.3 Defining the Fringes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103.4 Setting the Remaining Boundary Conditions . . . . . . . . . . . . . . . . . . . . . . 11

4 Running Wind-US 15

5 Results 17

iii

1 Introduction

This document describes the use of Wind-US to solve a problem using a Chimera, or overset,grid. It is primarily intended to demonstrate the use of GMAN for Chimera grids.1

The geometry is a 2-D airfoil with a flap, shown in Figure 1.

Figure 1: Airfoil/flap geometry.

Separate C grids have been created for the airfoil and the flap, with the flap grid overlaying theairfoil grid, as shown in Figure 2.

Figure 2: Original airfoil/flap grids.

The outer boundary of the airfoil grid actually extends far beyond the airfoil, but is expanded inFigure 2 to show the details near the surface. The two grids are contained in a multi-zone formattedPLOT3D xyz file. The airfoil grid is zone 1, with 205× 59 points, and the flap grid is zone 2, with179×33 points. In the figure, every other point in both directions, for both grids, has been omitted.

In the sections that follow:

• The cfcnvt utility is used to create a common grid (.cgd) file from the existing PLOT3D file.

• GMAN is used to cut a hole in the airfoil grid around the flap, define the fringe boundariesfor both grids, and set the remaining boundary conditions. This discussion makes up the bulkof the document.

• A Wind-US input data (.dat) file is created, and Wind-US is run to solve for the flow field.

• The resulting common flow (.cfl) file is used with CFPOST to create PLOT3D xyz and q files,and the results are displayed.

1The various files discussed in this document may be downloaded from the Wind-US documentation WWW site,at http://www.grc.nasa.gov/WWW/winddocs/gman/example/downloading.html.

1

http://www.grc.nasa.gov/WWW/winddocs/gman/example/downloading.html

2 Creating the .cgd File

The PLOT3D xyz file containing the overlayed grids is named demo.grid, and is a 3D (althoughwith kmax = 1), multi-zone, formatted, single-precision file without an IBLANK array. A .cgd filenamed demo.cgd was created using cfcnvt , as shown in the following runstream. Lines in slantedtype were typed by the user.

% cfcnvt***************************************************************************** Warning: This software contains technical data whose export is ** restricted by the Arms Export Control Act (Title 22, U.S.C., Sec 2751, ** et seq.) or Executive Order 12470. Violation of these export-control ** laws is subject to severe criminal penalties. Dissemination of this ** software is controlled under DoD Directive 5230.25 and AFI 61-204. *****************************************************************************

******* Common File Convert Utilities ******CFCNVT - Version 1.54 (last changed 2007/02/13 22:47:44)

0: Exit program2: Import a Common File3: Compress a Common File4: Break Common File into multiple transfer files5: Combine multiple transfer files into Common File6: Append one Common File to another7: Convert Common File binary to a text file8: Convert Common File text to a binary file11: Convert PLOT3D/Pegsus file to Common File12: Convert GASP file to Common File13: Convert OVERFLOW file to Common File14: Convert Common File to OVERFLOW file15: Convert CFPOST GPU file to Common File GPC16: Convert ascii rake to Common File rake CGF17: Convert Pegsus 4.0 files to Common File18: Convert Common File CFL to Plot3d Q

Enter the number from one of the above requests11

PLOT3D file type menu

0: Main menu1: Convert a PLOT3D Grid (.x) file to CFS.2: Convert a PLOT3D Solution (.q) file to CFS.3: Convert a PLOT3D Function (.f) file to CFS.


PLOT3D Number of Grids menu

0: Main menu

3

Airfoil/Flap Example Case

1: PLOT3D Single zone format.2: PLOT3D Multi zone format.


PLOT3D Zone dimension menu

0: Main menu1: PLOT3D 2d zone format.2: PLOT3D 3d zone format.


PLOT3D Format menu

0: Main menu1: PLOT3D Formatted (ASCII).2: PLOT3D Unformatted (sequential binary).3: PLOT3D Binary (c binary).


PLOT3D Iblank menu

0: Main menu1: PLOT3D grid with IBLANK format.2: PLOT3D grid without IBLANK format.


PLOT3D Precision menu

0: Main menu1: PLOT3D Single precision format.2: PLOT3D Double precision format.


PLOT3D INTOUT menu

0: Main menu1: No INTOUT/XINTOUT file.2: INTOUT file.3: XINTOUT file.

Enter the number from one of the above requests

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2 Creating the .cgd File

1Enter PLOT3D .x file to convert with suffix

demo.gridEnter output Common File name with suffix

demo.cgdzone, imax,jmax,kmax: 1 205 59 1zone, imax,jmax,kmax: 2 205 59 1Global maximums set as follows:mimax 205mjmax 59mkmax 1mpts: 12095recl: 563Processing zone ZONE 1Writing mesh dataimax,jmax,kmax: 205 59 1Processing zone ZONE 2Writing mesh dataimax,jmax,kmax: 179 33 1

0: Exit program2: Import a Common File3: Compress a Common File4: Break Common File into multiple transfer files5: Combine multiple transfer files into Common File6: Append one Common File to another7: Convert Common File binary to a text file8: Convert Common File text to a binary file11: Convert PLOT3D/Pegsus file to Common File12: Convert GASP file to Common File13: Convert OVERFLOW file to Common File14: Convert Common File to OVERFLOW file15: Convert CFPOST GPU file to Common File GPC16: Convert ascii rake to Common File rake CGF17: Convert Pegsus 4.0 files to Common File18: Convert Common File CFL to Plot3d Q


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3 Using GMAN

GMAN was then used in graphics mode to cut a hole in the airfoil grid around the flap, definethe fringe boundaries for both grids, and set the remaining boundary conditions. The file demo.jouis the journal file created during the interactive GMAN session, with the addition of commentsdescribing the procedure.

The first step, obviously, is to start GMAN.

gman

***** gman *****

Select the desired version from the following list.

0) END1) gman_pre optimized version

Single program automatically selected.

***************************************************************************** Warning: This software contains technical data whose export is ** restricted by the Arms Export Control Act (Title 22, U.S.C., Sec 2751, ** et seq.) or Executive Order 12470. Violation of these export-control ** laws is subject to severe criminal penalties. Dissemination of this ** software is controlled under DoD Directive 5230.25 and AFI 61-204. *****************************************************************************

GMANPRE - Version 6.163 (last changed 2007/02/14 16:35:41)Creating journal file ’gman.jou’.

Enter SWITCH or GRAPHICS to change to graphics mode.GMAN:

At this point, you could type @demo.jou to execute the commands stored in the journal filedemo.jou. You could also enter commands individually at the GMAN: prompt. Or, you could enterSWITCH or GRAPHICS to enter graphics mode.

The following sections describe in detail the use of GMAN for the airfoil/flap configuration. Thegraphics mode steps are on the left, with the Main Menu steps left-aligned and the Menu Optionsindented. Most of these are accomplished in GMAN by clicking on the listed menu item using theleft mouse button. A few require entering text in the prompt area at the bottom of the screen. (Seethe “Graphical User Interface Basics” section of the GMAN User’s Guide for a description of thevarious sections of the GMAN screen layout.)

The command line equivalents are shown on the right. Note that, in general, several graphicsmode steps become consolidated into a single command. A few of the commands are too long tofit on a single line, and are thus shown with the continued part indented. When using GMAN incommand-line mode, however, they should be entered on a single line.

3.1 Opening the File

We first need to tell GMAN the name of the file containing the grid.

7


Graphics Mode Command Line Mode

Common File FILE demo.cgdenter demo.cgd

3.2 Cutting the Hole

Next, we need to cut a hole in the airfoil grid surrounding the flap.

The first step is to select the zone containing the airfoil grid, and to select the “Overlapping”boundary type. (This boundary type is useful for setting boundary conditions on interior grid points,as well as for Chimera grids.)


BOUNDARY COND. ZONE 11: (from Zone List)OLAP BOUNDARY OLAP

We need to tell GMAN the procedure we’re going to use to define the hole. In this case the holewill be defined by grid surfaces that form a closed region around the flap.


MODIFY BNDY CUTTER SURFACE TYPESHOW OTHER ZONE

2: (from Zone List)PICK K-PLANE2

OLAP GENERATIONGENERATE HOLESSET/SHO CUTTER

CUTTER SURFACE

Next, we select the surfaces from the flap grid that specify a closed region around the flap definingthe hole.

The j = 1 surface in the flap grid (i.e., the flap surface itself) could be used. However, theflap grid is tightly packed near the flap surface to resolve the boundary layer, while the airfoil gridspacing in this region is much larger. Ideally, the exchange of information between the two gridsshould occur in regions where the grid cells are similar in size.

Using a grid line farther out, near the outer edge of the flap zone, would result in a hole biggerthan the flap grid. Since the boundary conditions around the hole for the solution in the airfoil zonewill be computed from the solution in the flap zone, this would be unacceptable.

For these reasons, the j = 26 grid line around the flap is used.

2At this point, you may want to adjust the view in the window by using the middle and right mouse buttons, orthe Center choice in the Display Options menu, to enlarge the the view around the flap.

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3 Using GMAN


SET SRF ZON CUTTER SURFACE IN ZONE 2 I20 J26 K1enter 2 TO I160 J26 K1 INCREMENT 1

SET SURF RANGEenter 20 26 1enter 160 26 1

SET SURF RANGE CUTTER SURFACE IN ZONE 2 I20 J1 K1enter 20 1 1 TO I20 J26 K1 INCREMENT 1enter 20 26 1

SET SURF RANGE CUTTER SURFACE IN ZONE 2 I160 J1 K1enter 160 1 1 TO I160 J26 K1 INCREMENT 1enter 160 26 1

The surfaces defining the hole cutter are shown in Figure 3, along with both grids in the region ofthe flap.

Figure 3: Surfaces defining hole cutter.

All overlapping boundaries and holes must have a unique label, greater than six. The Labelmenu choice is in the Subregion Selection area in the lower-right corner of the GMAN window.


Label LABEL 7enter 7

Finally, we can create the hole.


GENERATE HOLE GENERATE HOLE

The resulting airfoil grid, with the hole cut into it, is shown in the region of the flap in Figure 4.

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Figure 4: Airfoil grid with hole.

3.3 Defining the Fringes

The next step is to define the fringes and set boundary conditions on them. For the airfoil grid,the fringes will be defined as the hole boundary.


OLAP GENERATIONGENERATE FRINGE

FRG MODE HOLE FRINGE-MODE HOLEGENERATE FRINGE3 GENERATE FRINGEOLAP GENERATIONSET FRINGE BND SET FRINGE BOUNDARY COUPLED TOCOUPLE ZONE 2 BOUNDARY OLAP

2: (from Zone List)OLAP

COUPLEBOUNDARY COND. UPDATE

YES, SAVE CHANGES

The flap grid is completely embedded in the airfoil grid, and the outer boundaries do not overlapany solid boundaries. Cutting a hole is thus not necessary, and we can use the outer boundaries asthe fringe.

3From the Main Menu, not the Menu Trail

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3 Using GMAN


PICK ZONE/BNDY ZONE 22: (from Zone List) BOUNDARY OLAPOLAP

MODIFY BNDYGENERATE FRINGE

FRG MODE OUTERBOUND I1 ON FRINGE-MODE OUTER BOUNDARY ON I1BOUND IMAX ON FRINGE-MODE OUTER BOUNDARY ON IMAXBOUND JMAX ON FRINGE-MODE OUTER BOUNDARY ON JMAX

Label LABEL 8enter 8

GENERATE FRINGE4 GENERATE FRINGEOLAP GENERATIONSET FRINGE BND SET FRINGE BOUNDARY COUPLED TOCOUPLE ZONE 1 BOUNDARY OLAP

1: (from Zone List)OLAP

COUPLEBOUNDARY COND. UPDATE

YES, SAVE CHANGES

3.4 Setting the Remaining Boundary Conditions

The remaining boundary conditions that need to be set for the C grid around the airfoil are thedownstream outflow boundaries, the outer boundary, the C grid cut line, and the airfoil surface.The downstream and outer boundaries of the flap grid have already been coupled to the airfoil grid,so all that remain are the C grid cut line and the flap surface.

The downstream outflow boundaries for the airfoil grid are at I1 and IMAX, and are defined asoutflow boundaries.


PICK ZONE/BNDY ZONE 11: (from Zone List)I1 BOUNDARY I1

MODIFY BNDY OUTFLOWCHANGE ALL

OUTFLOWBOUNDARY COND. UPDATE

YES - UPDATE FILEPICK ZONE/BNDY

IMAX BOUNDARY IMAXMODIFY BNDY OUTFLOWCHANGE ALL

OUTFLOWBOUNDARY COND. UPDATE

YES - UPDATE FILE

4From the Main Menu, not the Menu Trail

11


The outer boundary of the airfoil grid is at JMAX, and is defined as a freestream boundary.


PICK ZONE/BNDYJMAX BOUNDARY JMAX

MODIFY BNDY FREESTREAMCHANGE ALL

FREESTREAMBOUNDARY COND. UPDATE

YES - UPDATE FILE

The C grid cut line and the airfoil surface are both at J1. First, we’ll couple the grid to itself,using “point match” coupling. This will define the cut line as a coupled boundary, leaving the pointson the airfoil surface undefined.


PICK ZONE/BNDYJ1 BOUNDARY J1

MODIFY BNDY CPMODE POINT MATCHCOUPLE COUPLED TO ZONE 1 BOUNDARY J1

1: (from Zone List)SET COUP MODE

POINT MTCH ONSEL OTHER BNDY

J1:COUPLE

Now, we’ll set a viscous wall condition at the remaining undefined points, and write the changesto the .cgd file.


CHANGE BY TYPE UNDEFINED IS VISCOUS WALLUNDEFINEDVISCOUS WALL

BOUNDARY COND. UPDATEYES - UPDATE FILE

Like the airfoil grid, the cut line and the flap surface in the flap grid are both at J1. The boundaryconditions there are set in the same way as in the airfoil grid.

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3 Using GMAN


PICK ZONE/BNDY2: (from Zone List) ZONE 2J1 BOUNDARY J1

MODIFY BNDY COUPLED TO ZONE 2 BOUNDARY J1COUPLE

2: (from Zone List)SEL OTHER BNDY

J1:COUPLECHANGE BY TYPE UNDEFINED IS VISCOUS WALL

UNDEFINEDVISCOUS WALL

BOUNDARY COND. UPDATEYES - UPDATE FILE

Finally, it’s a good idea to check the boundary conditions to make sure all is OK.5


TOPCHECK ZONE ALLCHECK BOUNDARY CHECK BOUNDARY

PICK ZONEALL (from Zone List)

RUN BNDY CHKS

After hitting the Enter key to return to graphics mode, we can quit GMAN.


END EXITYES - TERMINATE

5This checks regular (non-fringe) boundaries. Fringe boundaries can also be checked, using RUN FRNG CHKS ingraphics mode, or CHECK FRINGE in command line mode. Doing the fringe boundary check for this case yields severalmessages about volume ratios exceeding the tolerance. This is intended as a warning about differences in the sizes ofthe grid cells in the two zones in the area of the fringes. As noted earlier, the grid cells in this area should be similarin size. For this case, however, this does not seem to present a problem in the solution.

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4 Running Wind-US

Listed below is the input data (.dat) file demo.dat used for this case.

Demo of airfoil/flap Chimera gridMach 0.6First run

/ Inlet conditionsFreestream static 0.6 14.7 520. 0. 0.

/ Boundary conditionsDownstream pressure 14.7 zone 1

/ Viscous termsTurbulence sst

/ NumericsCycles 500

End

Two runs were made for a total of 1000 cycles (5000 iterations) On an SGI Octane R10000system, in serial mode, each run required just over 3200 seconds of CPU time. Genplot files for themaximum and L2 residuals were generated using resplt , as described in the “Tutorial” section of theWind-US User’s Guide.

The residuals are shown in Figure 5(a) and Figure 5(b).

0 1000 2000 3000 4000 5000 6000–6

–5

–4

–3

–2

–1

0

Iterations

Max

imum

Res

idua

l

Zone 1

Zone 2

(a) Maximum residual

0 1000 2000 3000 4000 5000 6000–6

–5

–4

–3

–2

–1

0

Iterations

Log

of

L2

Nor

m o

f R

esid

ual Zone 1

Zone 2

(b) L2 norm of the residual

Figure 5: Computed residuals.

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5 Results

Computed flow field results may be listed and/or plotted using CFPOST, as described in theCFPOST User’s Guide. CFPOST may also be used to create PLOT3D xyz and q files for use asinput to other post-processors, as described under “Examine the Results” in the “Tutorial” sectionof the Wind-US User’s Guide.

The computed results are shown in Figure 6 in the form of constant static pressure contours.

Figure 6: Computed static pressure contours.

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Airfoil/Flap Example Case

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